Interpretive Summary: The wheat genome contains an enormous diversity in organization, and variation in types of mating, which can play a role in our ability to manipulate the wheat genomes. A very important question is how the polyploid nature of wheat affects the genome organization and evolution of the species. The results of our study suggested that variation in types of polyploid formation impact the structure and expression of genes and chromosomes among the various grass species when they are combined to make a polyploid. This indicates that in their desire to transfer genes from one grass species to another, a breeder may be able to transfer the gene in question, but that gene may not be expressed when in a polyploid. This puts severe limitations on species-to-species gene transfer for agronomic improvement in cereals. Plant breeders will benefit from this information in their attempts to move genes between species toward improvement of crop productivity.

Technical Abstract:
Polyploidization-induced genome variation in triticale (X Triticosecale Wittmack) was investigated using both AFLP and RFLP analyses. The AFLP analyses were implemented with both EcoRI/MseI (E/M) and PstI/MseI (P/M) primer combinations, which, because of the relative differences in sensitivity to cytosine methylation, primarily amplify repetitive and low-copy sequences, respectively. The results showed that the genomic sequences in triticale involved a great degree of variation including both repetitive and low-copy sequences. The frequency of losing parental bands was much higher than the frequency of gaining novel bands, suggesting that sequence elimination might be a major force causing genome variation in triticale. In all cases, variation in E/M-primer-amplified parental bands was more frequent in triticale than variation from using P/M primers, suggesting that repetitive sequences were more involved in variation than low-copy sequences. The data also showed that wheat (Triticum ssp.) genomes were relatively highly conserved in triticales, especially in octoploid triticales, whereas the rye (Secale cereale L.) genome consistently demonstrated a very high level of genomic sequence variation (68-72%) regardless of the triticale ploidy levels or primers used. In addition, when a parental AFLP band was present in both wheat and rye, the tendency of the AFLP band to be present in triticale was much higher than when it was present in only one of the progenitors. Furthermore, the cDNA-probed RFLP analyses showed that over 97% of the wheat-coding sequences were maintained in triticale, while only about 61.6% of the rye-coding sequences were present in triticale, suggesting that the rye genome variation in triticale backgrounds included a great degree of rye-coding sequences. The data also suggested that concerted evolution might occur in the genomic sequences of triticale. In addition, the observed genome variation in wheat/rye addition lines was similar to that in triticale, suggesting that wheat/rye addition lines can be used to thoroughly study the genome evolution of polyploid triticale.